1. Field of Invention
The present invention relates to a magnetic device. More particularly, the present invention relates to a transformer.
2. Description of Related Art
Currently, a primary winding of a phase-shifting transformer is wound using layer winding. In layer winding, the wire is wound along the axial direction of magnetic core until the circumferential surface of the magnetic core is all wound by the wire. After that, the wire is moved outward along the radial direction and is then wound to form the next layer. Hence, the primary winding constitutes a plurality of concentric circle structures as viewed from the top. The secondary winding is mostly wound using disk winding. In disk winding, the wire is first wound around the magnetic core for one turn and is then wound outward along the radial direction. Hence, the second winding constitutes a spiral structure, such as a mosquito-repellant coil, as viewed from the top.
The uncoupled magnetic flux between the second windings and the first winding (that is the leakage flux) can generate inductive impedance that is the short-circuit impedance of the secondary windings. When a transformer is applied to a medium or high voltage inverter, a high short-circuit impedance is usually required to provide a certain amount of impedance if the medium or high voltage inverter is short-circuited. As a result, current overload problem is avoided. In view of the above, it is an issue desired to be resolved by those skilled in the art regarding how to increase the short-circuit impedance of secondary windings.